Uhm, what do you mean? When someone register not accept adf.ly ( know its no shortener, but dont remember the other names so i use this as example ) and the likes?
If so simply paste he offending shorteners to your url blacklist ( not exact matching ), so for example,
http://adfly.com and
http://www.adf.ly
Should deny then all urls containing this string
Cant add such things to the core to block by default, some may want to accept them